From Bill Fawcett's book:

Biographical sketch

LOUISA ALLETHA/ALETTA FALLENSTEIN (GAUSS) was born on April 20, 1813 to Henry Fallenstein and Charlotte Bessel in Lavern, Prussia. She was the niece of her Karl Gauss' good friend and fellow mathematician, Bessel. She married Charles William Gauss on August 21, 1833/37 in Germany, and soon after that they moved to St. Charles County, Missouri. She died on September 15, 1883 at St. Louis, Missouri.